28 February 2016

Asteroid news: NASA's update on 2013 TX68

Asteroid news: NASA's update on 2013 TX68
reported by  meteordetective
Link to article which was updated on Thu 25-Feb-2016 at 14:40 Pacific Time (22:40Z) and was originally posted on Tue 02-Feb-2016.

NASA have refined their "earlier flyby and distance predictions, reconfirming that the asteroid poses no threat to Earth."

But, the 'plot' thickens, as NASA has additionally "..identified an extremely remote chance that this small asteroid could impact on Sep. 28, 2017, with odds of no more than 1-in-250-million. Flybys in 2046 and 2097 have an even lower probability of impact."

I thought I'd investigate further and used Telnet to 'talk' to JPL's "Horizons" system.  However, as you can see (from the copy/paste below), there is no close-approach listed for 2017.  To be clear and specific, I instructed Horizons to show me all the known approaches from 01-Jan-2000 to 01-Jan-2200.

        Date (TDB)      Body   CA Dist  MinDist  MaxDist   Vrel  TCA3Sg  Nsigs  P_i/p
----------------------  -----  -------  -------  -------  ------ ------ ------ -------
A.D. 2001 Feb 12.30797  Venus  .075550  .029997  .430225  10.352 95321. 27737. .000000
A.D. 2013 Oct 13.34047  Earth  .013900  .013840  .013959  14.066   0.34 505.63 .000000
A.D. 2016 Mar 08.00436  Earth  .033383  .000207  .115301  15.324 8719.4 463.31 .000000
A.D. 2024 May 21.93046  Mars   .051950  .039661  .181328  15.950 8218.6 83319. .000000
A.D. 2028 Oct 22.29797  Earth  .092654  .010847  .254975  11.643 36290. 37681. .000000

If you access the asteroid's entry in JPL's SBDB, you'll see the following Close-Approach dates & times listed, which barely correspond to the Telnet session results (above).

2016-Mar-08 00:06, 2056-Sep-18 13:29, 2071-Sep-30 14:02, 2074-Feb-17 05:44, 2084-Oct-20 19:33, 2086-Oct-16 07:11, 2089-Feb-07 09:03, 2089-Mar-14 21:35.

Is something out of sync?

I'd initially intended to comment on the wide variance of 2013 TX68's potential close-approach distances (all relative to Earth's surface), which are remarkable and summarised below:

Nominal (the expected or 'should be' distance): 13.06 LD = 3,099,296.455 miles
Minimum: 0.08LD = 15,282.762 miles
Maxium: 45.09LD = 10,714,428.346 miles

(For reference, 1 LD --aka 1 Lunar Distance-- is equivalent to 382,500 kilometers / 239,062.5 miles (NASA)).

The difference between minimum and maximum values is 7,615,132 miles or 8.19% of the distance from Earth to the Sun...or also equivalent to 3,185.42% the distance from Earth to the Moon....which is a rather large value.

To add a further variable in to this situation, MPC have assigned 2013 TX68 a condition code of 8 for  its orbit uncertainty (10=highly uncertain and 0 = "good"), which is due to the fact that 2013 TX68 was only tracked for 3 days when it was initially discovered/observed - before it was 'lost' again.

Let me make myself perfectly clear:  I'm not suggesting 2013 TX68 will hit Earth, inferring it or stirring-up 'fear-porn'.  I'm just a little perplexed by the apparent of confusion --regarding when it will make its close-approaches to Earth-- and mentioning that there's a very wide margin of 'error' between the distances NASA are reporting for its 08-March-2016 close-approach.

Stay tuned!

Write to:
meteordetective AT gmail DOT com.

2016 The THIRD Year of "CERTAIN Uncertainty" ™ / Meteors, Asteroids, Comets, and MORE!!

1 comment:

aHEM again said...

I've also been trying to understand the changes being reported on 2013-TX68.

My primary question is whether the changes I list below are typical in your experience, rare, or unique? It seems strange that they would have decided to go include the original set of "pre-observations" in the first place. Then continuing to add "observations" implies to me confidence in the orbit to be able and go back and pick out further matches.

Why are they doing all of this?

All records I can access show NASA as reporting a 2016-Mar-05 flyby with a nominal pass @ 1.3 LD as of 2016-Feb-03 http://www.spaceweather.com/archive.php?view=1&day=03&month=02&year=2016 . That was apparently based on the original 3 days worth of observations.

Then around 2016-Feb-04 they added 7 days of "pre-observation" sightings. This resulted in a 2016-Mar-05 flyby with a nominal pass of 0.044 LD. http://www.spaceweather.com/archive.php?view=1&day=04&month=02&year=2016 .

Although they issued a story about this on the 5th http://www.jpl.nasa.gov/news/news.php?feature=4888 and spaceweather.com had a change in their tables, some NASA pages were still reporting the original data as of the 8th https://web.archive.org/web/20160208054926/http://neo.jpl.nasa.gov/ca/ .

Then on 2016-Mar-25 NASA updated their story @ http://www.jpl.nasa.gov/news/news.php?feature=4888 reporting that "new observations" had further refined the orbit to a 2016-Mar-08 flyby with a nominal pass of 13 LD and a min of 0.08 LD.

That's a awful lot of numbers changing in a short while, to still be saying how certain they are of everything.